A network of 250 treatment centres staffed by 10,000 therapists are needed urgently to tackle the epidemic of unhappiness that is Britain's "biggest social problem", a senior Government adviser says today.

The Labour peer and adviser to No 10, Lord Layard suggests that the psychological therapy centres should offer speedy access to treatment for mental problems in the same way as the fast track surgery centres for cataract and hip operations set up by the Government to cut NHS waiting lists.

In a lecture to be delivered to the Sainsbury Centre for Mental Health today, Lord Layard, former professor of economics at the London School of Economics, will say mental illness causes more suffering than poverty and unemployment.

"At any one time there are one million people with clinical depression and four million with clinical anxiety states. At present, people with depression or anxiety generally get pills or nothing. Only one in 10 people with these conditions get to see a therapist."

He added that there were still not enough therapists. "So a revolution is needed."